In a related art, it is proposed to develop a cell pattern layout capable of matching the shapes of ferroelectric elements and eventually increasing pairing properties thereof in a data holding device for storing data in a nonvolatile manner using the hysteresis characteristics of ferroelectric elements.
In the layout design of a semiconductor integrated circuit device, it is often the case that a dummy pattern is provided adjacent to a cell pattern to be used in order to suppress the etching loading effect attributable to the density (sparseness and denseness) of a mask pattern.
For example, if a memory array is formed on a semiconductor substrate, as shown in FIG. 30, dummy cells C identical in size with memory cells A and memory cells B are provided adjacent to the memory cells A such that the density of a mask pattern is not generated between the memory cells A arranged in the terminal end portions (mainly, the outer peripheral portions) of the memory array and the memory cells B arranged in the portions of the memory array other than the terminal end portions. Since the memory array is formed of a plurality of the memory cells A and B, the ratio of the area occupied by the dummy cells C to the total area of the memory array does not become so large even though the dummy cells C are identical in size with the memory cells A and the memory cells B.
However, if dummy elements Y and ferroelectric elements X, which are identical in size, are provided in a dada holding device employing a small number of (e.g., four) ferroelectric elements X as shown in FIG. 31, the ratio of the area occupied by the dummy elements Y to the total area of the data holding device becomes very large. For that reason, the size of the ferroelectric elements X should be small in order to avoid an enlargement of a chip area. This causes a problem because the reliability of the data holding device is lowered. In order to avoid the impairment of the reliability of the data holding device, the chip area itself needs to be increased, thereby increasing the manufacturing cost of the data holding device.